


Ultimate Betrayal

by DavidB1000



Category: Supergirl (TV 2015)
Genre: AU after season 3, Anger, Cheating, F/F, I'm Sorry, Please Don't Kill Me, This Is Why We Can't Have Nice Things, You'll hate me for this one, a moment of weakness
Language: English
Status: In-Progress
Published: 2018-11-21
Updated: 2018-11-21
Packaged: 2019-08-26 20:22:57
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 2,522
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/16688332
Author URL: https://archiveofourown.org/users/DavidB1000/pseuds/DavidB1000
Summary: After marrying Lena, Kara has to take a trip deep into space. When she returns she finds Lena in the arms of another woman. One Alex Danvers.





	1. Darkness

It had been one hell of an exhausting trip, saving a whole planet full of aliens by moving their planet around. Kara was looking forward to coming home, to spend time with Lena, her wife. A word that made her smile. After everything with Reign, and Sam, and the crazy cult, and learning her father had helped create the world-killers, a fact that her mother only reluctantly shared weeks after the battle with Reign, she finally learned that Lena knew Kara was Supergirl. She had also learned that Lena had did everything to help her, to make her stronger. Working to make Kara immune to Kryptonite.  
Eventually, James and Lena broke up, and Lena revealed her other secret, that she loved Kara.

Six months later, they were married. Kara was looking forward to coming back home and spending time with Lena. That was over a year ago. 

&^&

When she landed on the balcony of their penthouse apartment, Kara smiled. She slipped through the door by phasing through it, and walked towards the bedroom to surprise Lena. Her heartbeat was coming in strong if a bit fast-paced. 

She walked into the bedroom and started to speak as she turned her eyes towards the bed. Only to stop herself as she saw a familiar looking head of red hair poking out from under the covers, the owner of said red hair was moving around, kissing and touching Lena.  
“Oh...Alex.” Lena moaned. 

Kara blinked multiple times, cleared her eyes in case they were failing her, but the image did not change. Kara felt a surge of anger, but quickly squashed it. Being angry was something she could not afford to do based on how strong she was. She had moved a planet, getting upset now could endanger the entire Earth. And this betrayal by Lena and her own sister, adopted that she is, would not make her hurt other innocents.

She took a deep breath and spoke firmly. “I don't recall ordering a surprise threesome.”  
Alex yelped and jumped away from Lena, who stared directly at Kara. “OH! KARA! I CAN EXPLAIN!”

“Was she naked on the bed, and you tripped and fell face first into her vagina?” Kara asked. The joke was a bit tacky, she knew, but it was something Superman had learned from Lois. His sense of humor was not as squeaky clean as people thought.

Lena gasped. “Kara! I didn't mean to do this!”  
Alex groaned. “Kara. If you can't believe her, believe me, you know I would do nothing to hurt you. But you were gone for a long time.”

“It's been 3 months! Not 3 years! If it was 3 years I wouldn't even be mad! I would have just asked to join in!” Kara grumbled.

Alex winced. “Please, Kara, you can't believe we would hurt you on purpose!”

“Really?!” Kara groaned. “You're going to try to convince me you're not evil here?!

Alex cringed. “I'm not evil! I know this is bad.”

“Why would you sleep with my wife?!!” Kara growled. “Did you and Sam not work out?!” After the entire Reign fiasco, Sam only stayed because Ruby got Alex to admit her feelings for Sam.

Alex winced. “It's complicated.”

Lena shivered. “Kara, please. I know you're upset.”

“Upset?! Upset? I should put the both of you on the surface of Pluto without a space suit! You'll go blind first and then die a short time later!” Kara growled.

“Please don't punish us like that!” Lena gulped.

“I don't want to even talk to you right now!” Kara grumbled and turned around, and rushed away.

&^&

“I knew I'd find you here, Kara.” Superman spoke as he floated down and landed by Kara. Kara had sent him a message, and it had been several hours since she had found out Alex and Lena's betrayal.

She was currently sitting at the top of Mt. Rainier in Washington. She had always liked the view from a mountaintop. And Mt. Rainier was one of the farthest from Alex at the moment. Unless she wanted to go to Alaska. 

“I loved her!” Kara sobbed. She had been crying for almost the last few hours straight.  
Superman spoke. “The question you have to ask yourself, Kara, is what can you do about this?”

“I want to smack both of them across the Eastern Seaboard!” Kara grumbled.

“No you don't. You're just angry at the betrayal. I understand that.” Superman spoke.  
“How could you have suffered the same way I did? Lois only loves you!” Kara sobbed.

Superman said nothing for a moment. “I am truly sorry.”

&^&

“She ruined everything!” Kara yelled.  
Eliza Danvers winced. “I know you're upset. Believe me, I'm upset for you too.”  
It had been a few hours since Kara talked with Superman, and she had gone to her human mother, Alex's actual mother to talk to someone else.

“I just want to throw her to the moon!” Kara growled.

“While there is no doubt in my mind you could do that, I also understand you are too upset right now.” Eliza spoke softly.

Kara frowned. “Can't you disown her!”  
Eliza shook her head. “Despite my daughter's current insanely stupid mistake, I don't hate her. And in time, even your anger will fade.”

“Can I put her in the Marianas trench?” Kara pouted.  
“No.” Eliza shook her head. “Too messy.”

“Only if I left her down there for more than a few seconds.” Kara frowned.

&^&

When she landed on the balcony at L-Corp, Kara saw Lena and walked in. Lena yelped as she looked up and saw Kara.

Kara frowned. “I'm not going to kill you.”  
Lena relaxed slightly. “I wasn't worried so much about being killed as experiencing extreme gee forces.”

“I wouldn't accelerate you that fast. No matter how mad I was at someone. I might put you in Jupiter's red spot though.” Kara spoke.

“Please don't. I do not like being ripped apart by 1000 mile per hour windstorms.” Lena winced.

“I'm just still shocked that you did that to me.” Kara spoke.

“It was a horrible mistake, Kara. That's all I can say. We got a little too drunk.” Lena frowned. “I'm not a monster.” 

“I am not saying you are.” Kara spoke softly. “I just am upset. After everything we went through, Lena., everything, this is how you repay me?”

“I'm sorry!” Lena cried out.  
“I know. But apologizing an infinite amount won't change the pain this caused.” Kara frowned.

“I'd say you could smack me around, but let's face it, that wouldn't end well for me.” Lena winced.  
“I'm not going to hit you! I am most certainly not that angry.” Kara spoke firmly.

“I never thought I suggest beating me up either, but this has exposed new sides to all of us.” Lena frowned.

“The real downer is it was a matter of luck I came back when I did. A few days later, or a few days earlier, and it wouldn't have happened. Honestly, if you did sleep together, and I came back later, would I ever have known?” Kara asked.

“I probably would have told you eventually. The guilt...” Lena frowned.  
“And I would catapult Alex through a few different countries.” Kara spoke.

“Yeesh.” Lena winced.  
Kara took a deep breath. “You messed up, Lena. Big time.” 

&^&

Alex yelped as Kara phased through her front door. “Please don't kill me.”  
“I'm not.” Kara spoke firmly. “I am however temped to beat you like a red-headed stepchild.” 

Alex winced and touched her head of red hair. “Come on, Kara.”  
“I'm serious, Alex. I'm bloody furious here.” Kara grumbled.

“I get that, Kara, but let's face it, you'd kick my ass up and down the streets of this city and that's if I had Kryptonite on my side. It may weaken you, but your anger will override the pain.” Alex frowned.

“I am aware of how it works. I am so angry at what you did, though, that it will take a long time to smooth this over.” Kara grumbled and curled one hand into a fist. “I'm not going to let you walk away from this without a mark though. Thankfully it won't be the Scarlet Letter.” 

Alex winced. “I really don't want the letter A branded into my face/chest/arm/anywhere.”

Kara frowned. “I'm not going to brand the letter A into your forehead. As I said. I am going to make this hurt though.”

She outstretched her hand and started vibrating it faster than the human eye could see, creating a blurring motion. She put it up against Alex's head. “This won't kill you. But this will hurt like hell, I'm not going to lie.” 

Alex winced. “Kara...”  
She stopped as Kara phased the hand through Alex's head and into her brain, aiming for one specific spot in particular.

She was so much smarter than anyone gave her credit for. She moved a few atoms by vibrating in the right spot.  
Kara pulled her hand back out and Alex grunted and stumbled backwards. “What the hell did you do?”

“I altered the stroke you were going to have in a few days.” Kara spoke firmly.

“What the hell?!!” Alex yelped.  
“IT was going to be fatal. Now all I did is make sure it will hurt like hell. It won't cripple you, but you're not going to be up and around for a few weeks.” Kara spoke.

“How the hell can you figure out if I am going to have a stroke!?!” Alex yelped.  
“I placed it there when I was angrier.” Kara admitted.

Alex gasped. “What the hell!?”  
Kara winced. “It was not my finest moment, no.”

“You gave me a fatal stroke!?” Alex yelled.

“You slept with my wife and ruined my life and my marriage!” Kara yelled back, and the walls shook.

Alex winced. “Okay...”  
“Look, I did not mean to give you a fatal stroke. I was just so pissed off.” Kara frowned.

“Geez, I get that. I did not mean to do this!” Alex winced.  
“I need some time away from both you and Lena.” Kara spoke and rushed off.


	2. Light

**Summary for the Chapter:**

> Chapter 2! Kara fixes the stroke completely. Superman and her have a talk, and things get smoothed over for the most part.

“What the absolute Hell!?” Superman spoke as he landed before Kara.  
Kara winced. “Okay, I admit giving Alex a stroke was a bad idea.”

“Kara. I'm disappointed in your actions, but I do understand they were made in haste and anger. Look, if you figure out why Lena and Alex did this, you'll be able to move on.” Superman spoke.

“I want to move on. But Lena is scared of me.” Kara frowned.   
“You need to show them you will not kill them.” Superman spoke.

“I don't want to do that. I just, I was so upset and I made a big mistake there by trying to kill Alex.” Kara winced.

&^&

Kara landed at L-Corp's balcony and walked into Lena's office.  
Lena yelped slightly.  
Kara winced. “I am sorry. I am still angry at you, but I messed up when I hurt Alex more than you. I shouldn't have done what I did. And for that, I am sorry.”

Lena frowned. “I'm sorry for getting so damn drunk I thought it would be a good idea to have sex with Alex.”

“That's what I don't understand.” Kara frowned.

“Honestly, I don't understand it myself. I know that one does not just suddenly decide to cheat.” Lena frowned and her frown matched Kara's almost perfectly.

Kara said nothing. She looked around and then said. “I need to go.”

&^&

Kara found Alex in her apartment, looking extremely worried. Kara spoke. “Let me completely remove the stroke. It's not fair.”

Alex shivered and nodded. “You got a point there.”

Kara reached over and phased her hand into Alex's brain and fixed the blood clot before it could manifest as a stroke.

A moment later she removed her hand and said. “I am truly sorry I overreacted.”

“I know. Let's be honest, I can only beg your forgiveness for my transgression.” Alex spoke.

“I just wish things could be different.” Kara frowned.

“I know it was bad to sleep with Lena!” Alex spoke. “I just, when we got together that night, and we drank, and drank, I just felt myself relax around her. I had a crush on her. I can admit that now.” 

Kara frowned but said nothing. Alex nodded. “I know that it seems awkward, but I did. I had a crush on Lena, and I kissed her that night. That is what led to you catching us.”

“Be honest, was that the first time?” Kara asked.  
“Yes. I swear to you! I did not mean for this to happen.” Alex groaned.

“Alright. I can handle this. I am glad you explained yourself to me. I'm not upset as much as I was.” Kara spoke softly.

“I wish we could go back to the way things were.” Alex winced.

“Perhaps in time, I can forgive you two.” Kara spoke firmly.

“I can only hope that you can.” Alex spoke.

&^&

Lena looked up and for her credit did not jump when Kara walked in off the balcony at L-Corp.

Kara spoke. “I am so sorry. For my actions. I fixed the stroke I was giving Alex. She'll be fine. She explained all of this. I take it that 3 months away from me, you so desperately wanted to feel close to someone again that when Alex kissed you, and you were so drunk, that you got together from that.” 

Lena nodded. “Exactly! I truly did not mean to mess up like this. I love you so much, Kara. I couldn't imagine my life without you. I can only hope you'll forgive me someday.”

Kara spoke firmly. “In time, yes, I will forgive you. For now, I think we're still going to have to have a bit of time apart.”

“I understand.” Lena spoke.

&^&

“I managed to smooth things over with everyone, Kal.” Kara spoke as she landed on the roof of the Daily Planet.

“I'm glad.” Superman spoke.   
“I'm so sorry I messed up like I did and hurt Alex.” Kara spoke.  
“You made your decision in a moment of anger. No one is immune to anger. Not me, not you, not anyone.” Superman spoke.

Kara nodded. “I fixed the problem. Alex will be fine. I just, I didn't expect to walk in on that.”   
“I understand. It would not be something I'd want to walk in on either.” Superman spoke.

“I made that joke you learned from Lois when I caught them together when Alex said she could explain.” Kara spoke.

“I can understand that being the best time for that joke.” Superman spoke.  
“I just am so glad you never had these issues. Even if you would have handled them better.” Kara spoke.

“Well, I mean, if it was Lana that I caught Lois with I'd just clap my hands and say, 'Well played, you two.” Superman smiled.

Kara grinned and nodded. “Okay, I can see that. Thank you for making me feel better.”  
“I'll always make you feel better when you need it. We're family, Kara. I will always help my family.” Superman spoke.

**Notes for the Chapter:**

> Thank you all for being patient with this story. Well, everyone who was patient anyhow. :)  
> I hope you like this additional chapter.  
> Let me know if more needs to be added.

**Author's Note:**

> I've been working on this for a long time. I just didn't know when to put this up here. I figured now would be a good time.  
> Again, don't hate me for this.  
> I just wanted to put this up.  
> I think sometimes people do make horrible mistakes.


End file.
